This research investigates the influence of the Fama-French Five-Factor Model—comprising market risk premium, firm size, book-to-market equity, profitability, and investment—on green technology stock returns across developed and developing markets, specifically in Malaysia, the United States, and China. This quantitative study will use monthly time-series data from January 2017 to December 2023 to analyse the impact of the Fama-French Five Factors (FF5) on green tech stock returns in Malaysia, China, and the United States. Data will be sourced from S&P Capital IQ, and modern econometric software will be used to regress the independent variables (FF5 factors) on the dependent variable (portfolio returns). Since the study period includes the COVID-19 pandemic, this research also investigates how the pandemic influenced the relationships between risk factors and green tech stock returns. Using a comparative approach, it analyses the varying effects of the five risk factors on green tech stock returns in both emerging and developed economies. This analysis seeks to provide comprehensive insights into the risk-return dynamics of green tech investments, which are crucial for optimising investment portfolios in the face of climate change and economic disruptions caused by the pandemic. The findings of this study will offer valuable implications for investors, policymakers, and green tech companies, highlighting the importance of robust risk management and informed decision-making to foster sustainable financial and environmental outcomes.